Athletic said earlier on Thursday that they had rejected bid from United, even though it matched the figure stated in Herrera's release clause.

Old Trafford officials viewed it as a political stance from Bilbao, aimed merely at appeasing their own supporters.

"We aspire to have players whose first choice is to defend our shirt," said the Basque outfit in a statement on their own website. "Ander's decision doesn't match that, which is disappointing.

"It's not a pleasant moment, but it doesn't alter our philosophy nor our way of working."

Bilbao-born Herrera remains thankful to his home-town club.

Man Utd's most expensive buys

£37.1m: Juan Mata (from Chelsea) 2014

£30.75m: Dimitar Berbatov (Tottenham) 2008

£29.1m: Rio Ferdinand (Leeds) 2002

£29m: Ander Herrera (Athletic Bilbao) 2014

£28.1m: Juan Sebastian Veron (Lazio) 2001

£27.5m: Marouane Fellaini (Everton) 2013

£27m: Wayne Rooney (Everton) 2004

All fees approximate

"I will never forget my time with Athletic Club," he said. "I'd like to thank the fans and staff for all their support and above all wish all my fantastic former team-mates all the best for the future."

Herrera will report for pre-season training next month. It is anticipated he will be part of United's tour party when they head to the United States on 18 July.

"Ander is a fantastic young player, with great energy and creativity," said United assistant manager Ryan Giggs of the midfielder, who is yet to be given a squad number.

"We believe him to be one of the brightest young prospects in Spain and I am certain he will be a big hit with the United fans."

Though he is on World Cup duty with the Netherlands, Van Gaal has already had an impact, sanctioning contract extensions for winger Antonio Valencia and defender Patrice Evra.